PetSafe Magnetic Key with Adjustable Cat Collar Magnetic Key Cat Door For use with the PetSafe Magnetic Key Cat Door for additional pets to use the cat door or as a replacement key if your pet's key is lost Magnetic Key unlocks the flap from the outside so only your cat can enter your home Works with an unlimited number of Magentic Keys with no programming or batteries needed Includes 1 Magentic Key with split ring and 1 black adjustable cat collar Call, chat or email with our expert US-based customer care specialists six days a week; they are waiting to assist you and your pet with your product needs PetSafe Brand is an industry leading US manufacturer of pet behavior, containment, and lifestyle products since 1991, helping millions of people and pets each year